Lapping machine and method



Sept. 27, 1938. G. P. PASSMORE 2,131,638

LAPPING MACHINE AND METHOD Original Filed Jan. 30, 1937 4 Sheets-Sheet -l FIG-1.

INVENTOR GEORGE RPAssMoRs.

ATTORNEY Sept. 27, 1938. G. P. PASSMORE LAPPING MACHINE AND METHOD Original Fi led Jan. 50, 1937 4 Sheets-Sheet 2 INVENTOR Gsomz P. PASSMOREU WITNESSES:

W ATTORNEY Sept. 27, 1938. G. P. PASSMORE LAPPING MACHINE AND METHOD Original Filed Jan. 4 sheets-sheet 3 E R M m? E G R O E G ATTORN EY WITNESSES:

P 1938- I G. P. PASSMOR-E- 2,131,638

LAPPING MACHINE AND METHOD Original Filed Jan. 30, 1937 4 Sheets-Sheet 4 Y WITNESSES: I INVENTOR K GEORGE RPAssMoRE C M MAJ 0C W BY w,V%.(R-/-4' ATTORN EY Patented Sept. 27, 1938 UNITED STATES "PATENT OFFICE LAPPING MACHINE AND lVIETHOD Pennsylvania Application January 30, 1937, Serial No. 123,088 Renewed March 9, 1938 11 Claims.

My invention relates to lapping machines and it has for an object to provide improved apparatus of this character for lapping the abutting joint surfaces of machine parts.

A further object of my invention is to provide apparatus of the above character wherein lapping movement occurs over a widely varying path to assure uniformity of lapped surfaces and to prevent galling, which might occur with a fixed path of movement or where the same path is retraced too often.

The present invention is particularly applicable for lapping the horizontal joint surfaces of a steam turbine casing so as to provide surfaces having such high degree of smoothness and fitting relation that a steam-tight joint may be provided without the employment of a gasket. In the manufacture of upper and lower parts of the casing or cylinder of a turbine, the flanges are usually machined to provide planar joint surfaces, and it is customary to hand scrape the surfaces to remove machine marks and to secure smoother and better fitting surfaces so that, when the fiangesare bolted together, the required degree of steam tightness may be had. The procedure of hand scraping or lapping has not only been laborious but may cause undue delay in turbine manufacture. In accordance with the present invention, I have devised a machine which is operative to secure better and quicker lapping of abutting surfaces of the joint. The improved machine comprises a reciprocatory structure carried by bearings resting on fixed or stationary structure, the parts of the turbine casing or housing being arranged to be carried by the structures and the movable structure being adjustable with respect to the fixed structure suitably to lapping requirements. It is, therefore, a further object of my invention to provide apparatus of this character operating in the manner and for the purpose indicated.

A further object of my invention is to provide a machine of the above character with means for separating the stationary and reciprocatory supporting structures and to cause such structures to approach without affecting the lapping adjustment so that inspections may be made of the surfaces as lapping proceeds.

The above-recited and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a side elevation showing a turbine casing and a portion of the lapping apparatus;

Fig. 2 is a similar view showing the turbine cover held in raised position for inspecting the surfaces being iapped and for applying lapping compound;

Fig. 3 is a plan view of the turbine casing and the lapping apparatus; and

Fig. 4 is a diagram showing the path of movement of the cover effected by the lapping ape paratus.

Referring to the drawings in detail, I show a steam turbine casing IE] divided along the horizontal plane of the turbine axis of rotation into a base It and a cover l2, formed with flanges !3 and It for bolting them together. The upper surface of the base, indicated at E5, and the lower surface of the cover, indicated at iii, abut each other to form the joint between the base and the cover. These surfaces must be finished to a high degree of smoothness so as to fit each other closely to provide a joint tight against high steam pressure. Heretofore, such finishing has been done by hand scraping, which'is a timeconsuming and expensive procedure.

In accordance with the present invention, after the joint surfaces of the base and cover of the turbine casing are finish-machined, the base and the cover are mounted on lower and upper supporting structures of the lapping machine, the base H being set up on blocking I1 and shims l'l so. as to dispose the joint surface 15 in a horizontal plane. The upper or reciprocatory supporting structure of the machine includes a rail or beam l8 carrying the cover l2, the rail or beam being supported by means of slide bearings on pedestals arranged at either end thereof and forming parts of the lower supporting structure of the machine.

Each pedestal preferably includes a lower vertical cylinder 2| having a cylinder cover 22 extending beyond the cylinder to providea flange 22a having an upwardly-facing abutment surface 22?) and the pedestal carries a top plate 23 secured to the fixed or stationary lower bearing plate Z ta having an upper fiat bearing surface engaged by the lower flat bearing surface of the movable bearing plate 241), the movable bearing plate being slidablehorizontally in all directions. Lubricant under pressure is supplied to the bearing surfaces to maintain a film therebetween by any suitable means, a conduit 20 being diagrammatically indicated for this purpose. The pedestal also includes a plurality of jack screws 25, preferably four, equi-distantly spaced angularly about the axis of the cylinder, corrnected to and depending from. the top plate 23 and extending downwardly through openings 220 provided in the flange 22a. Nuts 26 are threaded on the screws 25 and they cooperate with the flange 22a to effect vertical adjustment of the pedestal topplate 23. Thus, it will be seen that, by suitable adjustment of the nuts 26 of the pedestals, the beam or rail l8 may be adjusted vertically to arrange the surfaces l5 and M3 for lapping.

In addition to adjustment of the base and cover suitably to lapping requirements, it is desirable that the cover shall be readily raised and lowered to permit of inspection of the surfaces as well as the placing of grinding compound therebetween without affecting the lapping adjustment. Accordingly, the pedestals include plungers 2'! fitting the cylinders 2| and having rod portions 28 abutting the pedestal top plates 23. If fluid under pressure is admitted to the lower portions of thecylinders, as by conduits 29, the plungers 21 will move upwardly thereby raising the bearings and the beam l8 together with the cover l2 sufliciently for the inspection purposes indicated. When fluid is allowed to exhaustfrom the cylinders, the plungers and associated parts will move downwardly, the pedeseffecting horizontal movement of the cover I2 for lapping. In accordance with the present invention, such movement is a composition or resultant of simple periodic or reciprocating movement in two directions perpendicular to each other, the periods or frequencies of the two simple movements being nearly but not exactly equal. In the illustrated embodiment, such apparatus comprises an eccentric 33, connected to the cover I2 through adjustable connecting links 34 bolted to the cover flange 14, for effecting longitudinal horizontal reciprocating movement of the cover. The eccentric 33 is driven by an electric motor 34 through reduction gearing 35, a bevel gear 36, and connecting shafting. Two eccentrics 38 are mounted in phase relation with each other on a common shaft 39 and are connected to a cover flange l4 through adjustable links 4| for effecting horizontal movement of the cover transversely thereof.

The shaft 39 is driven by a motor 42 through reduction gearing 43. The gear ratios of the gearing 35, 36, and 43 are such that eccentrics 33 and 38 rotate at speeds that are lust slightly different from each other. If desired, the motors 34 and 42 may be of the variable speed type and provided with variable resistances 44 for adjusting the speed ratios of the eccentrics.

Operation The base H is first set up with its joint surface l5 disposed horizontally. The cover is then mounted on the rail or beam l8 carried by the pedestal supports l9 and the latter are adjusted, by means of the jack screws 25 and nuts 26, so as to provide a predetermined close clearance between the joint surfaces. At the same time, either the cover or the base is adjusted angularly so as to bring the joint surfaces into parallel relation. This may be done in any one of several ways commonly employed for such adjustment; for example, the base may be adjusted to bring its joint surface l5 parallel with respect to the joint surface It of the cover by the interposing jacks or shims I? of proper thickness between the blocking I"! and the base. I prefer to provide an initial clearance of about .010 inch for the purpose of obtaining the parallel relation between the joint surfaces. Then, the nuts 26 are turned equal amounts to provide a reduced clearance, such as .002 inch, at which there may be high spots on the two surfaces just touching each other. If desired, the first-mentioned adjustment may be omitted and the jack screws initially adjusted to the second-mentioned adjustment.

The cover is then raised, as shown in Fig. by admitting fluid pressure to the cylinders 2| through the conduits 29, and grinding or lapping compound is applied to the joint surfaces. A mixture of conventional grinding compound and white lead is preferably used for this purpose, the function of the white lead being to provide lubrication. The cover is then lowered by exhausting the fluid pressure from the cylinders. The jack screw nuts then bear against the upper surface of the cover plate 22 so that the cover is supported through the rail Hi, the fulcrum blocks 3|, the bearing plates or members 24b and 24a, the pedestal top plate 23, the jack screws 25, the nuts 26, the cylinder cover plate 22, and the cylinders 2|. The nuts 26 having been previously locked in any suitable manner, the vertical adjustment of the pedestal supports is preserved, so that the joint surfaces l5 and I6 are returned to the proper relation.

The lapping action is then begun by energizing the motors 3G and 42 to drive the eccentrics. The eccentric 33 which moves the cover back and forth longitudinally, operates at a slightly different speed than the eccentrics 38 moving the cover transversely, so that reciprocating movement of the cover is effected longitudinally thereof at a rate or frequency slightly different from the reciprocating movement transversely thereof. The result of the difference in speed is that the cover does not move in a circular path as it would if they operated at the same speed and the stroke of the eccentrics were equal, or an elliptical path if the strokes were unequal.

An example of the resulting motion produced by different speeds of the eccentrics is graphically illustrated in Fig. 4. For the purpose of this illustration, the speed or frequency ratio of 10 to 11 has been arbitrarily chosen, but the nature of the movement is the same whenever the speeds are different. ment is represented by full lines and counterclockwise movement by dot and'dash lines.

Assuming that the eccentric which produces movement represented horizontally in Fig. 4 to be at the middle of its stroke and the eccentric that produces movement represented vertically to be at one end of its stroke, the position of any given point of the cover is represented at From this point, if the first-mentioned eccentric is moving to the right, the cover moves in clockwise direction, the path of movement being nearly circular upon leaving the point a. However, as the second-mentioned eccentric is travelling faster than the first, the path of travel gradually flattens about the diagonal extending from the upper left hand corner to the lower right hand corner, until at the point I), it again begins to round out, but travelling this time in counterclockwise direction as indicated by the dot and dash line. At the point b each ec- In this figure, clockwise movecentric is in the middle of its stroke. The path continues to become more nearly round until the point 0 is reached, at which point the first eccentric is again in the middle of its stroke and the second at the end of a stroke the second eccentric having advanced 180. From the point 0, the path again begins to flatten, this time about the diagonal extending from theupper right to the lower left corner of the figure until the point I) is again reached. The second eccentric has now advanced 270 ahead of the first eccentric since the point a, and at the point D both eccentrics are again in the middle of a stroke. The path again begins to round out, this time going in clockwise direction as represented by the solid line and continuing until the starting point a is again reached at which the path is most nearly round. At this point, there have been 10 revolutions of the first eccentric and 11 revolutions of the second eccentric. The point of the cover now retraces the same path represented in this figure.

It will be seen from Fig. 4 in the above description that the two speeds or rates of reciprocation produce a movement which starts from substantially circular movement in one direction gradually changing toward straight movement, then beginning to change toward circular movement in the other, then flattening out about the opposite diagonal and then rounding out again in the first direction.

The simple ratio of 10 to 11 has been chosen for illustration in order to make the figure relatively simple and so that the path may be more readily traced. However, a less simple ratio would produce a still more varied path of movement. For example, if the ratio of 10 to 10% were used, then, when there had been ten reciprocations in horizontal direction, there would have been 10 and reciprocations in vertical direction, so that the path of movement would not lead exactly to the point a, but would be somewhat displaced therefrom. The point a would not be reached and the path would not be retraced until there had been reciprocaticns horizontally and 43 vertically. In practicing my invention, I have found a ratio of about 20 to 21 to be very satisfactory.

The initial lapping action at the first adjustment, assumed as .002 inch in the present case, is continued for a relatively short time, such as ten minutes. The motors 34 and 42 are stopped and the cover is raised by applying fluid pressure to the cylinders 2! as already explained. The joint surfaces are inspected to see if there are any high spots at which the surfaces are contacting. This is indicated by the reduced thickness of the film of grinding or lapping compound and is readily ascertained by one skilled in the art. If there is contact, the lapping operation is resumed at the same adjustment. However, if there is no contact, all of the jack screw nuts 26 are turned down an equal amount for the purpose of reducing the clearance between the r joint surfaces tobring them into contact with the high spots. Whether adjustment is made or not, lapping compound is applied to the joint surfaces and the fluid pressure is released from the cylinders to lower the cover. The motors 34 and 42 are started and movement of the cover I2 is resumed.

The lapping operation then continues substantially as described. The cover is periodically raised after a suitable period of lapping operation for inspection of the joint surfaces and adjustment is. made or not in accordance with the result of the inspection. Thus, the cover is pearance of the surfaces, particularly with re' spect to the evenness of the grinding compound,

or it may be determined by the use of Prussian blue as is well known in the art.

From the foregoing, it willbe apparent that I have devised a lapping machine comprising a movable upper structure carried by bearings resting on a lower fixed structure, the structures being arranged to carry the machine parts whose mating surfaces are to be lapped. Thebearings are comprised by upper movable and lower fixed plate members having horizontal or planar bearing surfaces so that the upper supporting structure and the machine part carried thereby may be moved horizontally in all directions. The fixed or lower part of the machine includes pedestals, which, not only support the fixed or lower bearing plates, but also provide for adjustment of the bearings to adjust the surfaces of the machine parts suitably to lapping requirements. Furthermore, the pedestals preferably include hydraulic means to permit of ready separation of the machine parts for inspection of the surfaces as well as for placing of lapping of grinding compound thereon, after which the pedestals may be readily restored totheir adjusted portions or further adjustments thereof may be made. As already pointed out, translatory reciprocating motion is imparted to the upper supporting structure of the machine so as to effect lapping, such motion being preferably applied in two directions at right angles and at different frequencies so as to provide a widely varying path of lapping movement.

By the adjustment of the pedestal supports as described above, the joint pressure is relieved by supporting most of the weight of the cover on the pedestal supports, so that galling of the surfaces is avoided. a At the same time, the portion of the weight of the cover not taken by the pedestal supports provides. sufficient joint pressure for the lapping operation.

- While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior 1 art or as are specifically set forth in the appended claims.

What I claim is:

1. In a machine for lapping mating surfaces of first and second machine parts, stationary structure adapted to carry said first part, recip rocatory structure adapted to carry said second part, slide bearings between said structure and providing for relative translatory movements thereof, means providing for adjustment of themating surfaces of the machine parts suitably ond part, slide bearings between said structures;

and having flat bearing surfaces providing for relative translatory movements in all directions in the planes thereof, means providing for adjustment of the mating surfaces of the machine parts suitably to lapping requirements, and means for imparting translatory reciprocating movements to the reciprocatory structure.

3. In a machine for lapping mating planar surfaces of first and second machine parts, stationary structure adapted to carry said first part, reciprocatory structure adapted to carry said second part, slide bearings between said structures and providing for relative translatory movements thereof, means providing for relative adjustment of said structures to effect parallelism of the mating surfaces, means providing for adjustment of said mating surfaces suitably to lapping requirements, and means for imparting translatory reciprocating motion to the reciprocatory structure.

4. In a machine for lapping mating surfaces of first and second machine parts, stationary structure adapted to carry said first part, reciprocatory structure adapted to carry said second part, slide bearings between said structures and providing for relative translatory movements thereof, means providing for adjustment of the mating surfaces of the machine parts suitably to lapping requirements, means for separating said structures and causing them to approach to provide for inspection of the surfaces being lapped without affecting the adjustment of said clearance-varying means, and means for imparting translatory reciprocating movements to the reciprocatory structure.

5. In a machine for lapping mating planar surfaces of first and second machineparts, stationary structure adapted to carry said first part, reciprocatory structure adapted to carry said second part, slide bearings between said structures and providing for relative translatory movements thereof, means providing for adjustment of the mating surfaces of the machine parts suitably t0 lapping requirements, and first and second means for concurrently applying translatory reciprocating motion to the reciprocatory structure, the

direction of application of motion of the first means being at an angle with respect to that of the second means.

6. In a machine for lapping mating planar surfaces of first and second machine parts, stationary structure adapted to carry said first part, reciprocatory structure adapted to carry said second part, slide bearings between said structures and providing for relative translatory movements thereof, means providing for adjustment of the mating surfaces of the machine parts suitably to lapping requirements, first and second means for concurrently applying translatory reciprocating motion to the reciprocatory structure, the direction of application of motion from the first means being at an angle with respect to that of the second, and means providing for operation of said first and second means so that the frequencies of reciprocation thereof are different.

7. In a machine for lapping'horizontal joint surfaces of upper and lower machine parts, lower stationary structure adapted to carry said lower part, movable upper structure adapted to carry said upper part, slide bearings for supporting the upper structure on the lower structure and having fiat horizontal bearing surfaces providing for horizontal translatory movements of the upper structure in all directions, means providing for relative adjustment of the upper and lower machine parts to bring the joint surfaces into parallelism, means providing for adjustment of the joint surfaces suitably to lapping requirements, means for raising and lowering the upper structure without affecting 'the adjustment of the second-mentioned adjustment means, and means for imparting translatory reciprocating movements to the upper structure.

8. In a machine for lapping mating planar surfaces of first and second machine parts, a stationary structure including spaced pedestals and adapted to carry said first part in the space between the pedestals; reciprocatory structure adapted to carry said second part; bearings for supporting the reciprocatory structure on the pedestals and including fixed and movable plate members having fiat bearing surfaces; means for supplying lubricant to provide films between the bearing surfaces of each bearing; each pedestal including jack screws for transmitting load thrust thereto from the associated fixed bearing plate and providing for adjustment of the fixed bearing plate, whereby the fixed bearing plates may be adjusted to vary the adjustment of the mating surfaces suitably to lapping requirements; and means for imparting reciprocatory movements to the aggregate including the reciprocatory structure, the machine part carried thereby and the connected movable bearing plates.

9. In a machine for lapping mating planar surfaces of first and second machine parts, a stationary structure including spaced pedestals and adapted to carry said first part in the space between the pedestals; reciprocatory structure adapted to carry said second part; bearings for supporting the reciprocatory structure on the pedestals and including fixed and movable plate members having flat bearing surfaces; means for supplying lubricant to provide films between the bearing surfaces of each bearing; each pedestal including a cylinder having a flange provided with an abutment surface facing in the direction of the associated bearing, a plurality of screws having abutment relation with respect to the associated fixed bearing plate, nuts carried by the screws for engagement with said flange abutment surface and providing for adjustment of the associated fixed bearing plate, whereby the fixed bearing plates may be adjusted to vary the adjustment of the mating surfaces suitably to lapping requirements, and a plungerin the cylinder and having abutment relation with respect to the associated fixed bearing plate; means providing for the admission of fluid under pressure to the cylinders and the exhaust of fluid therefrom to effect movements of the plungers and to cause said bearings and the reciprocatory structure to move away from and toward the fixed structure; and means for imparting reciprocatory movements at right angles to the reciprocatorystructure.

10. In a machine for lapping mating horizontal joint surfaces of upper and lower machine parts, supporting structure for the lower part and including a pair of spaced pedestals; a beam structure for supporting the upper machine part; bearings for supporting the ends of the beam structure on the pedestals and including upper and lower plates having horizontal flat bearing surfaces;

means providing lubricant films between the surfaces of the bearings; means providing for vertical adjustment of the lower bearing plates with respect to the pedestals to adjust the joint surfaces suitably to lapping requirements; and means for imparting reciprocatory movements -to :the

aggregate including the upper machine part, the beam structure, and the upper bearing plates.

11. In a machine for lapping mating horizontal joint surfaces of upper and lower machine parts, supporting structure including a pair of spaced pedestals and arranged to carry the lower machine part in the space therebetween; a horizontal beam structure for supporting the upper machine part; bearings for supporting the ends of the beam structure on the pedestals; each bearing including movable upper and fixed lower plates having horizontal flat bearing surfaces; means providing lubricant films between the surfaces of the bearings; means providing for relative adjustment of the upper and lower machine parts to bring the joint surfaces into parallel relati0n;

each pedestal including a vertical cylinder having a flange provided with an upwardly-facing abutment surface, a plurality of vertical screws having their upper ends arranged in abutment relation with respect to the associated lower bearing plate and having their lower ends extending through openings provided in said abutment flange, nuts carried by the screws and engaging abutment relation with respect to the associated lower bearing plate; means providing for the admission of fluid under pressure to the cylinders and for the exhaust of fluid therefrom to cause the aggregate including the upper machine part, the

beam structure, and the bearings to move away from and toward the stationary supporting structure; first and second means for concurrently imparting reciprocatory movements to the aggregate including the upper machine part, the beam structure, and the upper bearing plates; the path of reciprocation of the first means being arranged at an angle to that of the second; and means providing for the operation of said first and second means such that the frequencies of reciprocation thereof are different.

GEORGE P. PASYSMORE. 

